Drive mechanism for jib cranes

ABSTRACT

An extensible jib for a crane comprising two jib sections arranged in telescopic relation with a pair of driven rollers engaging the inner section and operable to extend or retract the jib. Brake means are provided to hold the jib sections in any selected position, the brake means being operable in response to operation of the driven roller to release the brake when the rollers are driven and apply the brake when the rollers are not driven.

United States Patent 1191 Quick 14 1 Feb. 4, 1975 DRIVE MECHANISM FORJIB CRANES [75] Inventor: Donald J. Quick, West Bundaberg,

Queensland, Australia [73] Assignee: International Harvester Company,

Chicago, Ill.

[22] Filed; Oct. 9, 1973 [21] Appl. No.2 404,550

[30] Foreign Application Priority Data Oct. 9, 1972 Australia 748/72[52] U.S.Cl ..52/1l5,52/118,52/121, 212/144 [51] Int. Cl. B66c 23/64[58] Field of Search 52/111, 114, 117, 115, 52/118, 116, 121; 212/55,144; 214/141, 761, 762

[56] References Cited UNITED STATES PATENTS 1,611,326 12/1926 Abbe212/55 2,703,634 3/1955 Lee 52/115 2,992,710 7/1961 Thompson 52/1143,055,459 9/1962 Eitel 52/115 3,236,393 2/1966 Girardi 212/55' 3,319,8035/1967 Northcott 212/55 3,346,281 10/1967 Thompson..... 52/115 x3,465,904 9/1969 Pensa 214/141 x 3,480,109 11/1969 Eillel 212/553,670,465 6/1972 Cheze 52/115 3,800,965 4/1974 Barron 212/55 x FOREIGNPATENTS OR APPLICATIONS 970,879 9/1964 Great Britain 52/111 PrimaryExaminerErnest R. Purser Assistant Examiner-Leslie A. Braun Attorney,Agent, or Firm-Raymond E. Parks; Floyd B. Harman [57] ABSTRACT Anextensible jib for a crane comprising two jib sections arranged intelescopic relation with a pair of driven rollers engaging the innersection and operable to extend or retract the jib. Brake means areprovided to hold the jib sections in any selected position, the brakemeans being operable in response to operation of the driven roller torelease the brake when the rollers are driven and apply the brake whenthe rollers are not driven.

3 Claims, 4 Drawing Figures 1 DRIVE MECHANISM FOR JIB CRANES Thisinvention relates to an extension drive for a crane jib.

Many cranes are provided with an extendable jib, usually of a telescopicconstruction with rollers or slides provided at the front end of themain jib to support the extension portion. Hydraulic cylinders areusually mounted in line with, and behind the jib extension to effectextension and retraction thereof, and this restricts the practicallength of the jib extension.

It is an object of the present invention to provide a means foreffecting the movement of a jib extension which allows a maximum lengthof extension to be used.

Thus according to the present invention there is provided a drivemechanism for an extensible crane jib having a main jib section and anextension jib section arranged in a telescopic relation, said drivemechanism comprising at least two spaced rollers engaging opposite facesof the extension jib section, drive means coupled to at least one rollerto effecting movement of the extension jib section relative to the mainjib section to extend or retract the extension jib section, and brakemeans operable to lock the extension jib section relative to the mainjib extension and releasable in response to energisation of the drivemeans.

It is preferred that the drive means includes an hydraulic motor and thebrake means is adapted to be hydraulically released, the hydrauliccircuits of the motor and brake means are interconnected so that thebrake means is released when the motor is energised.

In the case where a hydraulic motor is used, the pressure required tooperate the hydraulic motor is also fed to a piston operated brake pad.The application of pressure releasing the pad from contact with theextension. In its normal position the brake is pressed against theextension jib section by a compressed spring. Thus if the hydraulicmotor is switched off or if a sudden pressure drop should occur, thebrake is immediately applied.

In a practical arrangement there is provided the hydraulic motor whichis operated by fluid pressure from the crane pump, and a valve isprovided to control the direction of rotation of the motor. A chain andsprocket drive connects the motor with a roller disposed on the upperside of the extension jib section and two rollers disposed on the lowerside thereof. The upper roller is supported on a frame pivotallysupported on the main jib section and is connected to a hydraulicalcylinder which is alos connected to the pressure line of the motor, sothat when the motor is operating the upper roller is pressed intodriving contact with the extension jib section. As an alternativearrangement, this hydraulic cylinder may be replaced by a spring load ofsufficient force to maintain the required driving contact.

The jib of the crane may be raised by increasing the inclination of thejib to the horizontal. As the inclination to the horizontal isincreased, the motor torque required to extend it will also increase,and the contact pressure between the rollers and the extension sectionwould decrease. By the use of the hydraulic cylinder to apply clampingpressure to the roller, the grip on the jib extension is maintained bythe hydraulic pressure in the motor circuit.

LII

It can be seen from the above that the present invention provides anextendable job drive mechanism which avoids the need for a hydraulicextension cylinder and allows for the incorporating of a longerextension section. Also the weight of the extension jib section, andhence the stability of the crane is not varied by the weight of thehydraulic fluid or the extension of the hydraulic ram as with prior artcranes.

The invention will be more readily understood from the followingdescription of one practical arrangement of a crane jib incorporating adrive and brake mechanism in accordance with the present invention. Thisarrangement of the jib is depicted in the accompanying drawings wherein:

FIG. I is a diagrammatic representation of a typical extendable cranejib located in the normal horizontal position;

FIG. 2 is a view similar to FIG. 1 with the jib in an elevated position;

FIG. 3 is an enlarged view of the forward end of the jib, partly insection, showing the drive and brake mechanisms;

FIG. 4 is a sectional view along line 4-4 in FIG. 3.

Referring now to the drawings, the jib crane comprises a main jib 6pivotally supported at 7 to the crane frame 8 with the lift cylinder 9,connected between the main jib 6 and a portion of the frame not shown,so that the main jib may be pivoted relative to the frame by extendingor retracting the cylinder 9.

Slidably supported within the main jib 6 is the jib extension 12 whichmay be extended or retracted in a telescopic fashion to vary theeffective length of the jib. The jib extension 12 is supported in themain jib l6 and guided during its movement by the stabilizing rollers 13supported in the main jib and the rollers 16,17 and 18 forming part ofthe drive mechanism 14 at the forward end of the main jib 6. The jibextension 12 rests on the rollers 17 and 18 so that the latter engagethe underface of the jib extension and the roller 16, which issubstantially vertical above the roller 17, engages the top face of thejib extension.

The main jib 6 is of a generally box type construction with the jibextension 12 located therein in a telescoped relation. The two rollers17 and 18 engaging the underside of the jib extension 12 are supportedin respective pairs of bearings 20 mounted in opposite sides of the mainjib. The roller 16 is supported in bearings 29 carried in respectivearms 28 located externally of the main jib 6. Each of the arms 28 arepivoted to the main jib 6 on a common axis 31, parallel to the axis ofthe roller 16. At the other end the arms 28 are interconnected by across member 32 extending through the main jib 6.

The single acting hydraulic cylinder 33 is attached to the main jib 6with the piston rod thereof connected to the cross member 32 so thatwhen fluid is applied to the hydraulic cylinder 33, the arms 28 pivotrelative to the main jib 6 to cause pressure engagement between theroller 16 and the upper face of the jib extension 12. The reaction tothe pressure applied through the roller 16 is taken by the rollers 17and 18 so that in effect the application of pressure to the hydrauliccylinder 33 causes pressure contact between the three rollers and thejib extension 12. The hydraulic cylinder 33 is interconnected with thehydraulic circuit of the motor 26 so that when the motor is operatedfluid under pressure is delivered to the hydraulic cylinder 33 so as toestablish pressure contact between the rollers and the jib extensionduring the driving operation.

Each roller has an axial extension at one end carrying respectivesprockets 21, 22 and 23 coupled by the chain 24 to the sprocket 25mounted on the shaft of the hydraulic motor 26. The chain 24 is engagedby the sprocket 21 driving the roller 16 on the external side of thechain, whilst the sprockets 22 and 23 driving the rollers 17 and 18engage the innerside of the chain so that rollers 17 and 18 rotate inthe opposite direction to the roller 16. As the roller 16 engages inopposite face of the jib extension, the three rollers in fact drive thejib in the same direction. The hydraulic motor 26 is reversible and iscontrolled by the valve 30 so that the jib extension may be extended orretracted by the operation of the hydraulic motor 26 driving the rollersl6, l7 and 18.

The brake mechanism comprises the back plate 36 carrying the frictionpad 37, and the hydraulic cylinder 38 connected via the piston rod 39 tothe back plate 36. The hydraulic cylinder 38 is rigidly attached to themain jib 6, and the pair of pressure springs 40 are interposed betweenthe cylinder and the pressure plate 42 carried by the piston rod 39. Thesprings 40 urge the friction pad via the back plate 36 and pressureplate 42 into frictional contact with the upper face of the jibextension 12, and thus acts as a brake to hold the jib extension 12 inthe desired position relative to the main jib 6. The hydraulic cylinder38 is a single acting cylinder with hydraulic fluid being admitted tothe underside of the piston as viewed in FIG. 3, to raise the piston,and hence raise the back plate and friction pad, against the action ofthe springs 40 to release the jib extension for extending or retractingmovement relative to the main jib.

The hydraulic cylinder 38 which releases the brake mechanism 35 isconnected to the hydraulic circuit of the motor 26 so that whenever themotor is operated to extend or retract the jib extension, fluid pressureis applied to the underside of the piston to raise the friction pad, andthus release the brake on the jib exten- SlOIl.

It will be appreciated that if the jib is upwardly inclined theextension would tend to retract under gravity without operation of themotor. However in order to release the brake, pressure is required inthe hydraulic circuit of the motor. Accordingly the one way pressurevalve 45 is provided in the return line 46 of the motor hydrauliccircuit so that any rotation of the motor will develop pressure in thereturn line sufficient to release the brake, and cause the rollers togrip the jib extension. This arrangement ensures that retraction of thejib extension is at all times under the control of the motor.

I claim:

1. In a crane having an elongated cantilevered main jib of the box typeconstruction, an extendable and retractable elongate extension jib ofuniform rectangular cross section telescopically mounted within the mainjib, hydraulic power means including means for selectively energizingthe power means for telescopically extending and retracting theextension jib, and securing means for holding the extension jib in placefollowing telescopic movement, the improvement comprising:

a U-shaped lever having the ends of the extending arms of the U hingedto the lateral sides of the main jib and the cross-member of the Upassing transversely through the lateral sides of the main jib;

a first roller mounted on a first shaft passing transversely through thelateral sides of the main jib and being journalled to the arms of theU-shaped lever, the first roller sitting on top of the extension jib;

a second roller mounted on a second shaft passing transversely throughand being journalled to the latteral sides of the main jib andsupporting the bottom of the extension jib, the axis of the second shaftbeing vertically aligned with the axis of the first shaft;

a third roller spaced horizontally from and parallel with the secondroller and being mounted on a third shaft passing transversely throughand being journalled to the lateral sides of the main jib and supportingthe bottom of the extension jib;

a pulley wheel keyed to each shaft including a continuous belt meansdrivingly connecting the pulley wheels to the hydraulic power means forrotating the rollers in unison and telescopically moving the extensionjib upon energization of the hydraulic power means;

a brake shoe sitting on top of the extension jib in the space betweenthe vertical planar axes of the second and third shafts;

first and second hydraulic power ram means mounted on the main jib andeach having first and second piston rod means respectively and beinghydraulically connected to the hydraulic power means for simultaneousenergization of the piston rod means with the power means, the firstpiston rod means being connected to the brake shoe for lifting the brakeshoe from the extension jib upon energization thereof, the second pistonrod means being connected to the cross-member of the U for swinging thearms of the U upon energization thereof and squeezing the extension jibbetween the rotating rollers; and

spring means between the brake shoe and the first piston rod means forpressing the brake shoe against the top of the extension jib upon thesimultaneous de-energization of the hydraulic power means and piston rodmeans for halting the movement of the extension jib.

2. In the combination, as claimed in claim 1, wherein the three rollersare of identical diameter and the pulley wheels for each shaft are ofidentical diameter.

3. In the combination, as claimed in claim 2, wherein the pulley wheelscomprise sprocket gears of identical size and the endless belt is achain trained about the sprocket gears, and the hydraulic power meansincludes a sprocket gear drivingly connected to the chain.

1. In a crane having an elongated cantilevered main jib of the box typeconstruction, an extendable and retractable elongate extension jib ofuniform rectangular cross section telescopically mounted within the mainjib, hydraulic power means including means for selectively energizingthe power means for telescopically extending and retracting theextension jib, and securing means for holding the extension jib in placefollowing telescopic movement, the improvement comprising: a U-shapedlever having the ends of the extending arms of the U hinged to thelateral sides of the main jib and the crossmember of the U passingtransversely through the lateral sides of the main jib; a first rollermounted on a first shaft passing transversely through the lateral sidesof the main jib and being journalled to the arms of the U-shaped lever,the first roller sitting on top of the extension jib; a second rollermounted on a second shaft passing transversely through and beingjournalled to the latteral sides of the main jib and supporting thebottom of the extension jib, the axis of the second shaft beingvertically aligned with the axis of thE first shaft; a third rollerspaced horizontally from and parallel with the second roller and beingmounted on a third shaft passing transversely through and beingjournalled to the lateral sides of the main jib and supporting thebottom of the extension jib; a pulley wheel keyed to each shaftincluding a continuous belt means drivingly connecting the pulley wheelsto the hydraulic power means for rotating the rollers in unison andtelescopically moving the extension jib upon energization of thehydraulic power means; a brake shoe sitting on top of the extension jibin the space between the vertical planar axes of the second and thirdshafts; first and second hydraulic power ram means mounted on the mainjib and each having first and second piston rod means respectively andbeing hydraulically connected to the hydraulic power means forsimultaneous energization of the piston rod means with the power means,the first piston rod means being connected to the brake shoe for liftingthe brake shoe from the extension jib upon energization thereof, thesecond piston rod means being connected to the cross-member of the U forswinging the arms of the U upon energization thereof and squeezing theextension jib between the rotating rollers; and spring means between thebrake shoe and the first piston rod means for pressing the brake shoeagainst the top of the extension jib upon the simultaneousde-energization of the hydraulic power means and piston rod means forhalting the movement of the extension jib.
 2. In the combination, asclaimed in claim 1, wherein the three rollers are of identical diameterand the pulley wheels for each shaft are of identical diameter.
 3. Inthe combination, as claimed in claim 2, wherein the pulley wheelscomprise sprocket gears of identical size and the endless belt is achain trained about the sprocket gears, and the hydraulic power meansincludes a sprocket gear drivingly connected to the chain.